Efficacy of cariprazine across symptom domains in patients with acute exacerbation of schizophrenia: Pooled analyses from 3 phase II/III studies

GABAergic and inflammatory changes in the frontal cortex following neonatal PCP plus isolation rearing, as a dual-hit neurodevelopmental model for schizophrenia

The pathogenesis of schizophrenia begins in early neurodevelopment and leads to excitatory-inhibitory imbalance. It is therefore essential that preclinical models used to understand disease, select drug targets and evaluate novel therapeutics encompass similar neurochemical deficits. One approach to improved preclinical modelling incorporates dual-hit neurodevelopmental insults, like neonatal administration of phencyclidine (PCP, to disrupt development of glutamatergic circuitry) then post-weaning isolation (Iso, to mimic adolescent social stress). We recently showed that male Lister-hooded rats exposed to PCP-Iso exhibit reduced hippocampal expression of the GABA interneuron marker calbindin. The current study expanded on this by investigating changes to additional populations of GABAergic interneurons in frontal cortical and hippocampal tissue from the same animals (by immunohistochemistry) as well as levels of GABA itself (via ELISA). Because inflammatory changes are also implicated in schizophrenia, we performed additional immunohistochemical evaluations of Iba-1 positive microglia as well as ELISA analysis of IL-6 in the same brain regions. Single-hit isolation-reared and dual-hit PCP-Iso rats both showed reduced parvalbumin immunoreactivity in the prelimbic/infralimbic region of the frontal cortex. However, this was more widespread in PCP-Iso, extending to the medial/ventral and lateral/dorsolateral orbitofrontal cortices. Loss of GABAergic markers was accompanied by increased microglial activation in the medial/ventral orbitofrontal cortices of PCP-Iso, together with frontal cortical IL-6 elevations not seen following single-hit isolation rearing. These findings enhance the face validity of PCP-Iso, and we advocate the use of this preclinical model for future evaluation of novel therapeutics-especially those designed to normalise excitatory-inhibitory imbalance or reduce neuroinflammation.

Adjunctive cariprazine as a novel effective strategy for treating major depressive disorder: A systematic review and meta-analysis

BACKGROUND

Cariprazine has been approved by the Food and Drug Administration for treating bipolar depression and as an adjunctive treatment for Major Depressive Disorder (MDD). However, it remains unclear about its pharmacological efficacy in treating MDD. Therefore, a meta-analysis was conducted to investigate the adjunctive use of cariprazine in MDD.

METHODS

Electronic databases were searched for eligible studies evaluating the efficacy and safety of cariprazine in patients with MDD up to November 15, 2023. The changes in Montgomery-Asberg Depression Rating Scale (MADRS) score and incidence of adverse events (AEs), which represents of efficacy and tolerability, are considered as the main outcomes.

RESULTS

A total of 3066 patients with MDD included in all across 5 RCTs. With regard to MADRS score, cariprazine group showed better results than control group (SMD = -0.12, 95% CI -0.19 to -0.04, P = 0.002, 5 RCTs, n = 3066). Cariprazine, meanwhile, improved the MADRS response (RR = 1.19, 95% CI 1.08 to 1.31, P = 0.0004, 5 RCTs, n = 3066). For safety outcomes, statistical difference was observed in AEs (RR = 1.26, 95% CI 1.18 to 1.35, P < 0.00001, 5 RCTs, n = 3077). The suicide ideation and SAEs showed no statistical difference between two groups.

CONCLUSION

Cariprazine demonstrated antidepressant effect as an augmentation therapy in treating MDD. Meanwhile, the tolerability of it was acceptable as an adjunctive treatment. However, studies with larger sample sizes are still needed to explore the optimal dosage.

The improvement of motor symptoms in Huntington's disease during cariprazine treatment

BACKGROUND

Huntington's disease (HD) is a progressive neurodegenerative disease, characterised by motor disturbances and non-motor (i.e., psychiatric) symptoms. Motor symptoms are the hallmark features of HD and take many forms. Their emergence is related to alterations in striatal dopaminergic neurotransmission: dopamine levels increase in the early stages of the disease, while more advanced stages are characterised by reduced dopamine levels. Such a biphasic change potentially explains the alterations in motor symptoms: increased dopamine-production induces hyperkinetic movements early in the disease course, while depleted dopamine storage leads to hypokinetic symptoms in the advanced phase. Dopamine D2-D3 partial agonists could be a promising treatment option in HD, as they have the potential to either elevate or lower the surrounding dopamine levels if the levels are too low or too high, respectively, potentially offering symptom-relief across the illness-course. Therefore, the present study aimed at exploring the effects of cariprazine, a dopamine D2-D3 partial agonist with high affinity to D3 receptors, on motor symptoms associated with HD.

METHODS

This was a single-centre, retrospective study where sixteen patients received off-label cariprazine treatment for 12 weeks (1.5-3 mg/day). Motor symptoms were evaluated using the Motor Assessment of the Unified Huntington's Disease Rating Scale. Least Square (LS) Mean Changes from Baseline (BL) to Week 8 and Week 12 in the Total Motor Score (TMS) were analysed using the Mixed Model for Repeated Measures method. In addition, improvement from BL to Week 8 and 12 was calculated for all motor items.

RESULTS

Data of 16 patients were collected, but data of only 15 patients were analysed as one patient dropped out due to non-compliance. Significant changes were observed from BL to Week 8 (LS Mean Change: -9.4, p < 0.0001) and to Week 12 (LS Mean Change: -12.8, p < 0.0001) in the TMS. The improvement was captured in the majority of motor functions, excluding bradykinesia and gait. Mild akathisia was the most commonly reported side-effect, affecting 3 patients.

CONCLUSION

This is the first study investigating the effectiveness of a D2-D3 partial agonist, cariprazine, in the treatment of HD. The findings of this study revealed that cariprazine was effective in the treatment of a wide range of motor symptoms associated with HD.

Adjunctive Cariprazine for the Treatment of Patients With Major Depressive Disorder: A Randomized, Double-Blind, Placebo-Controlled Phase 3 Study

OBJECTIVE

The purpose of this study was to investigate the efficacy of cariprazine, a dopamine D₃-preferring D₃/D₂ and serotonin 5-HT_1A receptor partial agonist, as adjunctive therapy for patients with major depressive disorder and nonresponse to at least one antidepressant monotherapy.

METHODS

In this double-blind placebo-controlled study, adults with major depressive disorder and inadequate response to antidepressants alone were randomized in a 1:1:1 ratio to placebo, cariprazine at 1.5 mg/day, or cariprazine at 3.0 mg/day. The primary outcome was change from baseline to week 6 in total score on the Montgomery-Åsberg Depression Rating Scale (MADRS). Least-squares mean differences were estimated in the modified intent-to-treat (mITT) population using a mixed-effects model for repeated measures with adjustment for multiple comparisons.

RESULTS

The mITT population comprised 751 patients (placebo: N=249; cariprazine 1.5 mg/day: N=250; cariprazine 3.0 mg/day: N=252). At week 6, the mean reduction from baseline in MADRS total score was significantly greater with cariprazine 1.5 mg/day than with placebo (-14.1 vs. -11.5) but not with cariprazine 3.0 mg/day (-13.1). Significant differences between the cariprazine 1.5 mg/day and placebo groups were also observed at weeks 2 and 4. Meeting the MADRS response criteria was significantly more likely among patients receiving cariprazine 1.5 mg/day than placebo (44.0% vs. 34.9%); remission rates were not significantly different among groups. Common treatment-emergent adverse events (≥5% in either cariprazine group and twice the placebo rate) were akathisia and nausea.

CONCLUSIONS

Adjunctive cariprazine at 1.5 mg/day demonstrated efficacy in reducing depressive symptoms in adults with major depressive disorder and inadequate response to antidepressants alone. Cariprazine was generally well tolerated, with a safety profile that was consistent with previous findings.

The efficacy and safety of cariprazine in the early and late stage of schizophrenia: a post hoc analysis of three randomized, placebo-controlled trials

BACKGROUND

The aim of the post hoc analysis was to better understand the efficacy and safety of cariprazine in patients with schizophrenia for less than 5 years (early stage) and for more than 15 years (late stage).

METHODS

Data from three phase II/III randomized, double-blind, placebo-controlled trials with similar design in patients with acute exacerbation of schizophrenia were pooled and patients with early and late stage of schizophrenia were determined. A mixed-effects model for repeated measures approach was applied and least square (LS) mean changes from baseline to week 6 on the Positive and Negative Syndrome Scale (PANSS) total and factor scores were reported. Descriptive statistics were used for safety analyses including treatment emergent adverse events (TEAEs) and discontinuation rates.

RESULTS

Overall, 460 patients were identified as being in the early and 414 in the late stage of schizophrenia. The pooled analysis evaluating mean change from baseline to week 6 in the PANSS total score indicated statistically significant difference between cariprazine and placebo in favor of cariprazine in both the early (LS mean difference [LSMD] -7.5 P < .001) and late stage (LSMD -6.7, P < .01) subpopulation. Early stage patients experienced similar amount of TEAEs (CAR 67.3%, PBO 54.1%) as patients in the late stage (CAR 69.6%, PBO 65.6%).

CONCLUSION

In conclusion, cariprazine, a potent D₃-D₂ partial agonist has been found to be safe and effective in the treatment of early and late stage schizophrenia.

Successful high dose antipsychotic treatment with cariprazine in patients on the schizophrenia spectrum: Real-world evidence from a Spanish hospital setting

Real-world evidence fills in an important gap by providing data on the effectiveness and tolerability of new medications in everyday patients. In this data collection form a Spanish hospital, the effectiveness and tolerability of cariprazine were evaluated in 14 patients who were admitted to the hospital due to an acute episode of schizophrenia or schizoaffective disorder. The collected data included demographic characteristics, history of disorder and previous treatment, and details of cariprazine therapy such as dosing, side effects and measurements of effectiveness via scales. Difference between admission and discharge on the Brief Psychiatric Rating Scale (BPRS) and Clinical Global Impression-Severity (CGI-S) scale scores were evaluated using the Wilcoxon Signed-Rank test. Significant improvement was detected in nearly all patients (one patient dropped out) as measured by the BPRS Total, Negative symptom, Positive symptom, and Hostility scores. At admission, patients were markedly-moderately ill and at discharge the severity was reduced to borderline ill and normal according to the CGI-S. The CGI-Improvement scale also indicated very much and much improvement at discharge. Importantly, patients left the hospital with high doses of cariprazine, i.e., 7.5 mg/day or even 9.0 mg/day, but this did not cause safety problems; cariprazine well-tolerated as only a few patients experienced side effects such as akathisia. The results provide novel evidence regarding the tolerability and effectiveness of cariprazine in high doses patients on the schizophrenia spectrum.

Limitations of access to antipsychotics in Canada: loss of the old and unavailability of the new options

Schizophrenia is a severe, debilitating disorder that is associated with a significant burden of illness. Antipsychotic medications remain the mainstay of treatment for schizophrenia and related disorders. In recent years, a number of new psychotropic medications have been introduced to the market, with some potential differences in the mechanism of action compared to the previous ones. In this paper, we discuss the issue of lack of access to the newer antipsychotics in Canada, and the discontinuation of some of the older options from the market, leaving clinicians and patients with a limited number of available options. While the aim of this paper is to increase awareness of the current state of availability and accessibility of options, we further discuss some potential solutions.

Remission of Persistent Negative Symptoms and Psychosocial Consequences by Combined Clozapine and Cariprazine Treatment in a Patient With Long-Standing Treatment-Resistant Schizoaffective Disorder

This patient case report describes a 45-year old white unmarried man with disability pension due to schizoaffective disorder, diagnosed at the age of 24. He lives in an apartment and has housing support. Retrospectively, the patient displayed prodromal markers of a disorder within the schizophrenia spectrum many years before the onset of frank psychosis, indeed since childhood. Over the years several symptoms and signs across schizophrenia domains have been manifest: positive, negative, cognitive, and affective, among which the negative and affective symptoms and signs were the earliest to appear. While the positive, disorganized, and catatonic symptoms responded to treatment - when duly tested and complied with - the negative and affective symptoms have been notoriously difficult to handle. We now report on the successful introduction of cariprazine (CAR) to his ongoing clozapine (CLZ) medication, the result of which has been a near-complete remission of his persistent negative and psychosocial issues. We interpret this remarkable alleviation of the patient's disease - and concomitant improvement of his quality of life - in terms of neuroreceptor target complementarity between CLZ and CAR, with particular emphasis on the contributions from the D3 and D2 receptor partial agonist components of the latter agent.

Case Report: Long-Acting Oral Cariprazine

Introduction

Cariprazine is a third-generation antipsychotic, approved for the treatment of schizophrenia and bipolar disorder and used off-label for schizoaffective disorder and treatment-resistant depression. Cariprazine is a partial agonist at dopamine receptors D2 and D3 and serotonin receptor 5HT1A and an antagonist at serotonin receptors 5HT2B and 5HT2A. It is metabolized by CYP3A4 in desmetyl-cariprazine and didesmethyl-cariprazine, both active metabolites with a half-life of 1-2 days and 2-3 weeks, respectively.

Case Report

Here we show the cases of 3 outpatients diagnosed with bipolar I disorder (two patients) and schizoaffective disorder (one patients) and characterized by low adherence to treatment, satisfactory cognitive and personal functioning and average disease severity to whom we administered cariprazine as a monotherapy, on a two-times a week schedule (i.e., every 72-96 h). We evaluated response to treatment and disease remission according to conventional definitions, using rating scales BPRS, PANSS and BDI-II. Two-times a week treatment was set either after a disease relapse (one patient), after a sustained remission obtained with daily administration of cariprazine (one patient) or since our first evaluation (one patient). After 4 weeks of treatment all three patients satisfied criteria for response to treatment and remission, a result that was sustained for 8 (in one patients) and 12 months (in other two patients) and still ongoing.

Discussion

Reported results support our hypothesis that long half-lives of cariprazine and its metabolites provide an adequate therapeutic response with a two-times a week administration. In selected patients, cariprazine administered as a "oral long-acting" seems effective in treating acute episodes of illness and in sustaining remission, combining advantages of oral and long-acting injectable antipsychotics concerning therapeutic alliance.

Real-Life Clinical Experience With Cariprazine: A Systematic Review of Case Studies

Background

The hierarchy of evidence coming from evidence-based medicine favors meta-analyses and randomized controlled trials over observational studies and clinical cases. Nonetheless, in the field of psychiatry, where conditions are much more complex, additional evidence coming from real-world clinical practice is necessary to complement data from these gold standards. Thus, in this systematic review, the aim is to summarize the evidence coming from clinical case reports regarding cariprazine, a third-generation antipsychotic drug that has been approved for the treatment of schizophrenia and bipolar I disorder with manic, depressive or mixed features in adults.

Methods

A systematic review was performed using Embase and Pubmed databases searching for English-language cases published in peer-reviewed journals between 2000 January and 2021 September with the following search terms: (cariprazin* OR "rgh-188" OR rgh188 OR vraylar OR reagila) AND ("case report*" OR "case report"/de OR "case stud*" OR "case study"/de OR "case seri*").

Results

After the removal of duplicates, 49 articles were retrieved via the search, from which 22 were suitable for this review. These 22 articles encompassed 38 cases from which 71% described patients with schizophrenia, 16% patients with psychotic disorders, 5% patients with mood disorder and 8% described patients with other disorders such as Wernicke-Korsakoff syndrome, borderline personality disorder and obsessive-compulsive disorder with paranoid schizophrenia. The median age of patients was 31, and half of them were female. The majority of patients (76%) started cariprazine with 1.5 mg/day, and the most common maintenance dose was 4.5 mg/day (34%) and 3.0 mg/day (29%).

Conclusion

Cariprazine was found to be safe and effective in a wide range of psychiatric conditions with different symptom profiles from acute psychotic symptoms through addiction to negative and cognitive symptoms. The results are in-line with the established evidence from clinical trials, however, they also show how cariprazine can be successfully utilized for treating certain symptoms irrespective of the indication.

The efficacy of cariprazine on cognition: a post hoc analysis from phase II/III clinical trials in bipolar mania, bipolar depression, and schizophrenia

OBJECTIVE

To investigate the effect of cariprazine on cognitive symptom change across bipolar I disorder and schizophrenia.

METHODS

Post hoc analyses of 3- to 8-week pivotal studies in bipolar I depression and mania were conducted; one schizophrenia trial including the Cognitive Drug Research System attention battery was also analyzed. Outcomes of interest: Montgomery-Åsberg Depression Rating Scale [MADRS], Functioning Assessment Short Test [FAST], Positive and Negative Syndrome Scale [PANSS]). LSMDs in change from baseline to end of study were reported in the overall intent-to-treat population and in patient subsets with specified levels of baseline cognitive symptoms or performance.

RESULTS

In patients with bipolar depression and at least mild cognitive symptoms, LSMDs were statistically significant for cariprazine vs placebo on MADRS item 6 (3 studies; 1.5 mg=-0.5 [P<.001]; 3 mg/d=-0.2 [P<.05]) and on the FAST Cognitive subscale (1 study; 1.5 mg/d=-1.4; P=.0039). In patients with bipolar mania and at least mild cognitive symptoms, the LSMD in PANSS Cognitive subscale score was statistically significant for cariprazine vs placebo (3 studies; -2.1; P=.001). In patients with schizophrenia and high cognitive impairment, improvement in power of attention was observed for cariprazine 3 mg/d vs placebo (P=.0080), but not for cariprazine 6 mg/d; improvement in continuity of attention was observed for cariprazine 3 mg/d (P=.0012) and 6 mg/d (P=.0073).

CONCLUSION

These post hoc analyses provide preliminary evidence of greater improvements for cariprazine vs placebo across cognitive measures in patients with bipolar I depression and mania, and schizophrenia, suggesting potential benefits for cariprazine in treating cognitive symptoms.

Symptomatic Profile of Cariprazine in the Context of ICD-11 Domains for Schizophrenia: Review of Clinically Oriented Studies: Симптоматический профиль карипразина в контексте доменов шизофрении в МКБ -11: обзор клинически ориентированных исследований

INTRODUCTION

One of the innovations in the ICD-11grouping "Schizophrenia and Other Primary Psychotic Disorders" is the implementation of six symptom domains intended to improve diagnostics and treatment of these mental conditions in clinical practice. In this respect, evaluation of the effects of various psychotropic drugs, primarily antipsychotic agents, on the specified psychotic symptom domains is a critical task. The antipsychotic agent cariprazine, registered in many countries worldwide (including Russia) for schizophrenia treatment, was selected as the psychotropic drug model for the purposes of the present review.

METHODS

For the purposes of this review the MEDLINE, Cochrane Central Register of Controlled Trials, and PubMed databases were searched for randomized controlled trials comparing cariprazine with a placebo, or a placebo and one or several antipsychotic agents, and that was performed within the period from January 2014 to March 2021.

RESULTS

Cariprazine has proved its efficiency in relation to all symptom groups of the ICD-11 domain "Positive Symptoms", and may be considered a front-line therapy for treatment of the first and multiple episodes of schizophrenia, disorganized thinking, and behavioral disorders in the form of aggressiveness and hostility. Cariprazine has the best evidential base for treatment of various symptoms within the ICD-11 domain "Negative Symptoms" among all antipsychotic agents. The data with regard to the effects of cariprazine on the domain "Depressive Mood Symptoms" are controversial. No data concerning the effects of cariprazine on the domain "Manic Mood Symptoms" are available, but the effectiveness of cariprazine monotherapy for manic episodes without any psychomotor agitation signs in the instance of bipolar disorder has been demonstrated. The effectiveness of cariprazine therapy for the ICD-11 domain "Psychomotor Symptoms" has not been investigated, either within the framework of monotherapy or in the course of adjuvant therapy. The effectiveness of cariprazine has been demonstrated in treatment of the domain "Cognitive Symptoms", and the pro-cognitive effect of the drug has developed regardless of its impact on any other schizophrenia symptoms. The drug's capability to improve the functioning of patients with schizophrenia was demonstrated regardless of the impact on psychotic symptoms.

CONCLUSION

Cariprazine is the first-line drug for treatment of the domain "Negative Symptoms" as well as representing front-line therapy for the treatment of ICD-11 domains "Positive Symptoms" and "Cognitive Symptoms". Additional studies will be required in order to evaluate the effects of cariprazine on the ICD-11 domains "Manic Mood Symptoms" and "Depressive Mood Symptoms".

Dosing Cariprazine Within and Beyond Clinical Trials: Recommendations for the Treatment of Schizophrenia

Although the optimal dosing of an antipsychotic medication is known to be essential in the long-term management of schizophrenia, in case of novel drugs such as cariprazine, determining the right dosing strategy is not that simple. Without decades of experience with a particular compound, evidence regarding dosing and titration comes primarily from double-blind, placebo controlled clinical trials that are not necessarily mirroring the real-life experiences of doctors. Via summarizing data from both clinical data (n = 3275) and real-world evidence (observational study n = 116, case studies n = 29), this perspective paper aims to shed a light on the appropriate dosing strategies of cariprazine from treatment initiation through switching strategies to concomitant medications.

Case Report: Functional and Symptomatic Improvement With Cariprazine in Various Psychiatric Patients: A Case Series

Cariprazine is a third-generation antipsychotic medication approved for the treatment of schizophrenia and bipolar disorder, with unique pharmacodynamic and pharmacokinetic properties. In this case series, the functional and symptomatic improvement of three patients who had been diagnosed with different psychiatric disorders and who exhibited various symptoms from psychotic to mood symptoms is described. The first case is about a young male patient with bipolar disorder and cocaine abuse who managed to become abstinent from cariprazine. The second and third cases describe patients with psychosis suffering from positive, cognitive and mood symptoms who were non-adherent to previous medication. In both cases, cariprazine was well-tolerated and effective in alleviating symptoms, thus improving their everyday functioning as well. In the discussion, the associations between symptom domains and the receptor profile of cariprazine are also highlighted, providing an explanation of the observed effects. It is concluded that cariprazine is a good treatment option for patients with symptoms of psychosis and addiction; is well-tolerated without the induction of side effects such as weight gain or sedation; and is appropriate for patients who have problems with adherence.

New Antipsychotic Medications in the Last Decade

PURPOSE OF REVIEW

Over the last ten years, the treatment of psychosis has seen a near explosion of creative development in both novel agents and new delivery modalities. The current review summarizes these developments over the past decade (2011-2020). We performed a systematic review utilizing PubMed and PsychInfo with the aim of identifying all the RCT and related analyses in adults with psychosis (schizophrenia and mania).

RECENT FINDINGS

We identified 11 significant developments: the introduction of new antipsychotics cariprazine, brexpiprazole, lumateperone, and pimavanserin; introduction of new delivery methods: subcutaneous long-acting risperidone, aripiprazole lauroxil, transdermal asenapine, and inhaled loxapine; and the introduction of new approaches such as olanzapine/samidorphan for olanzapine-associated weight gain, examination of the TAAR1 agonist SEP 363,856 as a test of concept, and the combination of Xanomeline/Trospium, an M₁ and M₄ muscarinic receptor agonist in conjunction with a peripheral anticholinergic. Last decade has seen a tremendous development in second-generation antipsychotics which provides unprecedented treatment options for clinicians in treating psychosis.

Treatment of Symptom Clusters in Schizophrenia, Bipolar Disorder and Major Depressive Disorder With the Dopamine D3/D2 Preferring Partial Agonist Cariprazine

Cariprazine is currently approved for the treatment of patients with schizophrenia (USA and EU), and for manic, depressive, and episodes with mixed features in bipolar I disorder (USA): several randomized controlled studies have also explored its efficacy in patients with major depressive disorder. This review summarizes its current therapeutic uses and potential advantages for treating the main symptoms of schizophrenia, bipolar I and major depressive disorder, considering its pharmacodynamic properties, efficacy, and tolerability. Its predominantly D3 receptor preferring affinity, with functional selectivity according to the prevailing neuronal environment, contributes to its efficacy across a wide array of psychopathological symptoms (including reality distortion, disorganized thought, negative symptoms, mood disturbance, anhedonia, and cognitive impairment), and to a favorable side effect profile. Cariprazine may be a "drug of choice" in patients with predominant negative and cognitive symptoms of schizophrenia, as well as those with metabolic syndrome. Further investigation of its relative efficacy when compared to aripiprazole or other active comparators is warranted. Its effectiveness in the treatment of bipolar mania, bipolar I depression and bipolar I episodes with mixed features, with minimal accompanying metabolic changes is well-established. The longer half-life and delayed time to relapse in patients diagnosed with schizophrenia when compared to other second-generation antipsychotics represent other advantages, given the high rates of non-adherence and frequent relapses seen in clinical practice. Its efficacy in overlapping symptom domains in other major psychiatric disorders appears promising.

Developments in Biological Mechanisms and Treatments for Negative Symptoms and Cognitive Dysfunction of Schizophrenia

The causal mechanisms and treatment for the negative symptoms and cognitive dysfunction in schizophrenia are the main issues attracting the attention of psychiatrists over the last decade. The first part of this review summarizes the pathogenesis of schizophrenia, especially the negative symptoms and cognitive dysfunction from the perspectives of genetics and epigenetics. The second part describes the novel medications and several advanced physical therapies (e.g., transcranial magnetic stimulation and transcranial direct current stimulation) for the negative symptoms and cognitive dysfunction that will optimize the therapeutic strategy for patients with schizophrenia in future.

Cariprazine, A Broad-Spectrum Antipsychotic for the Treatment of Schizophrenia: Pharmacology, Efficacy, and Safety

Schizophrenia is characterized by positive, negative, cognitive, and affective symptoms. Antipsychotic medications, which work by blocking the dopamine D₂ receptor, are the foundation of pharmacotherapy for schizophrenia to control positive symptoms. Cariprazine is a dopamine D₃ receptor-preferring D₃/D₂ partial agonist antipsychotic that is approved for the treatment of schizophrenia (USA and European Union [EU]) and manic and depressive episodes associated with bipolar I disorder (USA). Partial agonist agents have a lower intrinsic activity at receptors than full agonists, so they act as either functional agonists or functional antagonists depending on the surrounding neurotransmitter environment. Beyond efficacy against positive symptoms, the unique D₃-preferring partial agonist pharmacology of cariprazine suggests potential advantages against negative symptoms, and cognitive and functional impairment, which are challenging to treat. The efficacy and safety of cariprazine in adult patients with schizophrenia have been demonstrated in four short-term randomized, double-blind, placebo-controlled clinical trials, two long-term open-label studies, one relapse prevention study, and one prospective negative symptom study versus the active comparator risperidone. Additional post hoc investigations have supported efficacy across individual symptoms and domains in schizophrenia, as well as in diverse areas of interest including cognition, functioning, negative symptoms, hostility, and global well-being. This comprehensive review of cariprazine summarizes its pharmacologic profile, clinical trial evidence, and post hoc investigations. Collective evidence suggests that the pharmacology of cariprazine may offer broad-spectrum efficacy advantages for patients with schizophrenia, including effects against difficult-to-treat negative and cognitive symptoms, as well as functional improvements. Cariprazine was generally safe and well tolerated in patients with short- and long-term exposure and no new safety concerns were associated with longer-duration treatment.

Trial registration ClinicalTrials.gov identifiers, NCT00404573, NCT00694707, NCT01104766, NCT01104779, NCT01412060, NCT00839852, NCT01104792.

Current perspectives in treating negative symptoms of schizophrenia: A narrative review (Review)

The negative symptoms of schizophrenia are an unmet treatment target as currently approved treatments mostly control positive symptoms. The persistence of these symptoms holds back the patient's reinstatement in society, making them incapable of fulfilling their social, professional, or family roles. There is overwhelming research evidence suggesting that the negative symptoms of schizophrenia are associated with poorer functioning and lower quality of life than positive symptoms, confirming the need for developing new treatments for this particular category of symptoms. This present review aims to review clinical trials addressing novel pharmacological approaches addressing primary negative symptoms of schizophrenia. We overview both monotherapies, first-generation and second-generation antipsychotics, and add-on therapies, including psychostimulants, anti-inflammatory drugs, antidepressants, molecules targeting glutamatergic, cholinergic or serotonergic systems and hormones. Our findings suggest that the primary negative symptoms of schizophrenia may be mitigated by adjunctive therapies, and we highlight the pharmacological agents that have proven superior efficacy. Novel compounds such as cariprazine and MIN-101, to date, show promising results, but large clinical trials are needed to test their efficacy and safety.

Cariprazine as a therapeutic option for schizophrenia: a drug evaluation

Introduction: Schizophrenia is a very disabling condition that may result in a significant impairment of individual, professional, and social adjustments. Antipsychotics (APs), the first-line treatment for schizophrenia, in many cases modify the course of the disease, by reducing the institutionalization risk, at the price of severe and invalidating side effects. Cariprazine is one of the latest second-generation APs (SGAs) acting as a partial agonist of type 2 and 3 dopamine receptors, which was recently approved for the treatment of adult schizophrenia.Areas covered: The authors provide a critical review and commentary on the currently available data on the effectiveness and tolerability of cariprazine in schizophrenic patients, with a particular focus on its specific target symptoms.Expert opinion: Cariprazine appears significantly effective on both acute and maintenance treatment of schizophrenia, and in improving positive, negative, and cognitive symptoms, slightly more than other SGAs. It shows a good safety and tolerability profile, with akathisia being its most common side effect. Although further independent studies are needed to clarify its precise advantages over other SGAs, cariprazine seems a promising compound not only in schizophrenia, but also in a broad range of psychiatric conditions, including perhaps bipolar and addictive disorders.

Cariprazine Use in Early Psychosis: Three Case Reports

Objective: Cariprazine is a new atypical antipsychotic approved for the acute and maintenance treatment of schizophrenia (1, 2) and for the treatment of manic or mixed episodes associated with bipolar I disorder (1). Recently, cariprazine also got extended FDA-approval for the treatment of depressive episodes in adults with bipolar I disorder (3). The use of low doses of atypical antipsychotics is an essential component of early intervention in psychosis. For its particular performance and tolerability, cariprazine is becoming an important option for the treatment of first-episode psychosis. Method: Three patients experiencing first-episode psychosis (FEP) were successfully treated with cariprazine. Two patients were in their first months of the disease, and the third patient was in his third year after the FEP. Results: The three patients had a diagnosis of non-affective FEP, which includes schizophrenia, delusional disorder, and schizoaffective disorder. One of them was in their third year after the FEP with a predominance of negative symptoms at this stage of the disorder. All the patients were treated with cariprazine with a target dose of 3-4.5 mg/day. The three patients showed improvements in their psychosis, including a decrease in negative symptoms. No significant side effects were reported. Conclusion: Our three case reports indicate that cariprazine is an atypical antipsychotic beneficial in the treatment of early psychosis. Treatment with low doses of cariprazine could be effective and tolerable in this phase of the disorder. Future studies with longer follow-up of FEP patients are recommended to confirm these positive results of cariprazine in the early phases of psychosis.

Improving Mood and Cognitive Symptoms in Huntington's Disease With Cariprazine Treatment

In Huntington's disease (HD), the main clinical symptoms include depression, apathy, cognitive deficits, motor deficiencies and involuntary movements. Cognitive, mood and behavioral changes may precede motor symptoms by up to 15 years. The treatment of these diverse symptoms is challenging. Tetrabenazine and deutetrabenazine are the only medications specifically approved for Huntington's chorea, but they do not affect the non-motor symptoms. For these, antidepressants, antipsychotics, and benzodiazepines have demonstrated benefit in some cases and can be used off-label. These drugs, due to sedative side effects, may negatively influence cognition. Sixteen patients having HD received a 12-week off-label cariprazine (CAR) treatment (1.5-3 mg/day). Cognitive performance and behavioral changes were measured by the Addenbrooke Cognitive Examination (ACE) test, the Cognitive and Behavioral part of the Unified Huntington's Disease Rating Scale (UHDRS), and the Beck Depression Inventory (BDI). Mixed model for repeated measures was fitted to the data, with terms of visit, baseline (BL) and their interaction. Cariprazine treatment resulted in the following changes from BL to week 12, respectively: the mean score of BDI decreased from 17.7 ± 10.7 to 10.0 ± 10.7 (p <0.0097), while the Behavioral Assessment score of the UHDRS decreased from 54.9 ± 11.3 to 32.5 ± 15.4 (p < 0.0001); ACE score increased from 75.1 ± 11.0 to 89.0 ± 9.3 (p < 0.0001); Cognitive Verbal Fluency score from 6.2 ± 2.5 to 7.7 ± 2.7 (p < 0.0103); Symbol Digit Test from 9.2 ± 6.9 to 12.3 ± 8.9 (p < 0.0009). Mild akathisia was the most frequent side effect, presenting in 2 out of 16 patients (12.5%). We conclude that CAR had a positive effect on depressive mood, apathy and cognitive functions in patients with early stage of HD. Based on the neurobiological basis of these symptoms, CAR can improve the dopamine imbalance of the prefrontal cortex. This draws attention to the transdiagnostic approach which supports the further understanding of the similar symptomatology of different neuropsychiatric disorders and helps to identify new indications of pharmaceutical compounds.

Case Report: Cariprazine in a Patient With Schizophrenia, Substance Abuse, and Cognitive Dysfunction

This case report describes a 30-year old male diagnosed with schizophrenia at the age of 23, and with a long history of drug abuse. He had previously received a wide range of antipsychotic drug treatment regimens, all with some degree of effect, but never with complete symptom relief. He was also suffering from persistent cognitive and negative symptoms. At the time of admission in our clinic, he was on Quetiapine (QUE) and Haloperidol (HAL). It was therefore decided to substitute HAL for Cariprazine (CAR)-an agent with a novel pharmacological and clinical profile-in the hope of gaining increased efficacy, particularly in the cognitive and negative symptom domains. Within 3 weeks of the switch from HAL to CAR the patient clearly improved, and notably so in the aforementioned symptom areas. A number of subsequent adjustments of antipsychotic dosages and adjunct medications during the ensuing months resulted in an apparently more stable alleviation of positive as well as negative and cognitive symptoms, including markedly improved personal and social capabilities. Interestingly, some time after initiating CAR treatment the patient also reported that from being a heavy smoker (60 cig/d) he had cut down and eventually ceased smoking entirely; furthermore, he has remained clean of other substance abuse since his first admission in 2020. The joint treatment with CAR in combination with QUE thus seems to have improved the patient's cognitive functioning as well as possibly his susceptibility to substance abuse.

Effects of Brexpiprazole Across Symptom Domains in Patients With Schizophrenia: Post Hoc Analysis of Short- and Long-Term Studies

The successful treatment of schizophrenia entails improvement across a spectrum of symptoms. The aim of this post hoc analysis was to characterize the short- and long-term effects of brexpiprazole on Positive and Negative Syndrome Scale (PANSS) ‘Marder factors.’ Data were included from three 6-week, randomized, double-blind, placebo-controlled studies; a 52-week, randomized, double-blind, placebo-controlled maintenance treatment study; and two 52-week open-label extension (OLEx) studies—all in schizophrenia (DSM-IV-TR criteria). Patients receiving oral brexpiprazole were dosed at 2–4 mg/day (short-term studies) or 1–4 mg/day (long-term studies). At Week 6, least squares mean differences (LSMDs, with 95% confidence limits [CLs]) for brexpiprazole (n = 868) vs placebo (n = 517) were: Positive symptoms: −1.55 (−2.30, −0.80), P < .0001, Cohen’s d effect size (ES) = 0.27; Negative symptoms: −1.12 (−1.63, −0.61), P < .0001, ES = 0.29; Disorganized thought: −1.26 (−1.78, −0.74), P < .0001, ES = 0.32; Uncontrolled hostility/excitement: −0.76 (−1.15, −0.37), P = .0002, ES = 0.26; Anxiety/ depression: −0.56 (−0.91, −0.22), P = .0014, ES = 0.22. At last visit of the maintenance study, LSMDs (95% CLs) for brexpiprazole (n = 96) vs placebo (n = 104) were: Positive symptoms: −3.44 (−4.99, −1.89), P < .0001, ES = 0.62; Negative symptoms: −1.23 (−2.52, 0.07), P = .063, ES = 0.27; Disorganized thought: −1.69 (−2.81, −0.56), P = .0035, ES = 0.42; Uncontrolled hostility/excitement: −1.26 (−2.12, −0.39), P = .0046, ES = 0.41; Anxiety/depression: −0.72 (−1.47, 0.03), P = .061, ES = 0.27. In the OLEx studies, improvements were maintained over 58 (6 + 52) weeks of brexpiprazole treatment. In conclusion, these data suggest that brexpiprazole treats the continuum of schizophrenia symptoms, in the short- and long-term. Trial Registration: Data used in this post hoc analysis came from ClinicalTrials.gov identifiers: NCT01396421, NCT01393613, NCT01810380, NCT01668797, NCT01397786, NCT01810783.

The More, the Merrier…? Antipsychotic Polypharmacy Treatment Strategies in Schizophrenia From a Pharmacology Perspective

Antipsychotic polypharmacy/drug combination treatment (APP) is a remarkably common practice in the schizophrenia context, given the lack of general support in treatment Guidelines. There is also a vast literature on APP outcomes, but a paucity of high-quality evidence-based data to guide and optimize adequate use of APP. This seems particularly true regarding many pharmacology-based considerations involved in APP treatment strategies. This paper first briefly summarizes clinical literature related to the use of APP. Against this backdrop, the pharmacological target profile features are then described of frequently used antipsychotic agents, in relation to estimated free plasma exposure levels at clinically efficacious dosing. APP strategies based on the properties of these drugs are then scrutinized and gauged within the background literature framework. The anticipated usefulness of APP from the pharmacological standpoint is detailed regarding efficacy, adverse effect (AE)/tolerability, and safety perspective, including why, when, and how it may be used to its advantage. For the purpose, a number of theoretically beneficial combinations as well as instances with suboptimal-and even futile-APP approaches are exemplified and discussed from the rational pharmacodynamic and pharmacokinetic pros and cons point-of-view. In this exposé, particular attention is paid to the utility and features of 3rd Generation Antipsychotic dopamine (DA) D2-D3 agonists within an APP setting.

Cariprazine in the management of negative symptoms of schizophrenia: state of the art and future perspectives

In schizophrenia, dopaminergic hyperactivity in the mesolimbic regions, or possibly even selectively so in the dorsal striatum, seems to cause the emergence of psychotic symptoms, whereas dopaminergic hypoactivity in cortical regions underlies the negative symptoms and cognitive deficits. Managing the negative symptoms is a major current challenge in the treatment of schizophrenia with a dearth of novel modalities to address this clinical issue. Cariprazine is a novel second-generation antipsychotic that specifically targets the D3 receptor mainly associated to negative symptoms. The review summarizes the main issues regarding negative symptom management and the role of cariprazine treatment.

Maintenance treatment with antipsychotic drugs for schizophrenia

BACKGROUND

The symptoms and signs of schizophrenia have been linked to high levels of dopamine in specific areas of the brain (limbic system). Antipsychotic drugs block the transmission of dopamine in the brain and reduce the acute symptoms of the disorder. An original version of the current review, published in 2012, examined whether antipsychotic drugs are also effective for relapse prevention. This is the updated version of the aforesaid review.

OBJECTIVES

To review the effects of maintaining antipsychotic drugs for people with schizophrenia compared to withdrawing these agents.

SEARCH METHODS

We searched the Cochrane Schizophrenia Group's Study-Based Register of Trials including the registries of clinical trials (12 November 2008, 10 October 2017, 3 July 2018, 11 September 2019).

SELECTION CRITERIA

We included all randomised trials comparing maintenance treatment with antipsychotic drugs and placebo for people with schizophrenia or schizophrenia-like psychoses.

DATA COLLECTION AND ANALYSIS

We extracted data independently. For dichotomous data we calculated risk ratios (RR) and their 95% confidence intervals (CIs) on an intention-to-treat basis based on a random-effects model. For continuous data, we calculated mean differences (MD) or standardised mean differences (SMD), again based on a random-effects model.

MAIN RESULTS

The review currently includes 75 randomised controlled trials (RCTs) involving 9145 participants comparing antipsychotic medication with placebo. The trials were published from 1959 to 2017 and their size ranged between 14 and 420 participants. In many studies the methods of randomisation, allocation and blinding were poorly reported. However, restricting the analysis to studies at low risk of bias gave similar results. Although this and other potential sources of bias limited the overall quality, the efficacy of antipsychotic drugs for maintenance treatment in schizophrenia was clear. Antipsychotic drugs were more effective than placebo in preventing relapse at seven to 12 months (primary outcome; drug 24% versus placebo 61%, 30 RCTs, n = 4249, RR 0.38, 95% CI 0.32 to 0.45, number needed to treat for an additional beneficial outcome (NNTB) 3, 95% CI 2 to 3; high-certainty evidence). Hospitalisation was also reduced, however, the baseline risk was lower (drug 7% versus placebo 18%, 21 RCTs, n = 3558, RR 0.43, 95% CI 0.32 to 0.57, NNTB 8, 95% CI 6 to 14; high-certainty evidence). More participants in the placebo group than in the antipsychotic drug group left the studies early due to any reason (at seven to 12 months: drug 36% versus placebo 62%, 24 RCTs, n = 3951, RR 0.56, 95% CI 0.48 to 0.65, NNTB 4, 95% CI 3 to 5; high-certainty evidence) and due to inefficacy of treatment (at seven to 12 months: drug 18% versus placebo 46%, 24 RCTs, n = 3951, RR 0.37, 95% CI 0.31 to 0.44, NNTB 3, 95% CI 3 to 4). Quality of life might be better in drug-treated participants (7 RCTs, n = 1573 SMD -0.32, 95% CI to -0.57 to -0.07; low-certainty evidence); probably the same for social functioning (15 RCTs, n = 3588, SMD -0.43, 95% CI -0.53 to -0.34; moderate-certainty evidence). Underpowered data revealed no evidence of a difference between groups for the outcome 'Death due to suicide' (drug 0.04% versus placebo 0.1%, 19 RCTs, n = 4634, RR 0.60, 95% CI 0.12 to 2.97,low-certainty evidence) and for the number of participants in employment (at 9 to 15 months, drug 39% versus placebo 34%, 3 RCTs, n = 593, RR 1.08, 95% CI 0.82 to 1.41, low certainty evidence). Antipsychotic drugs (as a group and irrespective of duration) were associated with more participants experiencing movement disorders (e.g. at least one movement disorder: drug 14% versus placebo 8%, 29 RCTs, n = 5276, RR 1.52, 95% CI 1.25 to 1.85, number needed to treat for an additional harmful outcome (NNTH) 20, 95% CI 14 to 50), sedation (drug 8% versus placebo 5%, 18 RCTs, n = 4078, RR 1.52, 95% CI 1.24 to 1.86, NNTH 50, 95% CI not significant), and weight gain (drug 9% versus placebo 6%, 19 RCTs, n = 4767, RR 1.69, 95% CI 1.21 to 2.35, NNTH 25, 95% CI 20 to 50).

AUTHORS' CONCLUSIONS

For people with schizophrenia, the evidence suggests that maintenance on antipsychotic drugs prevents relapse to a much greater extent than placebo for approximately up to two years of follow-up. This effect must be weighed against the adverse effects of antipsychotic drugs. Future studies should better clarify the long-term morbidity and mortality associated with these drugs.

[Negative and positive disorders of schizophrenia (issues of co-dependence, psychopathology and pathogenesis)]

The authors consider current and own conceptions about correlations of the processes underlying the pathogenesis of schizophrenia presented by negative and positive disorders. With growth of academic psychiatry, evaluation of a correlation between positive and negative dimensions has changed dramatically: on the one hand presenting in clinical unity - simultaneous psychopathologic structures, and on the other hand being clinically and pathogenetically heterogenic in dimensional structure. According to our clinical and biological findings and an analysis of fundamental neurobiological studies, positive and negative disorders present in the clinical picture of schizophrenia as two separate psychopathological and pathogenetic structures. A new paradigm of the correlation between positive and negative structures - the interaction between positive and deficit symptoms - reveals psychopathological functions differentiated for each of dimensional structures. Negative disorders act as «transformers» modifying characteristics of primary transnosological positive disorders to the level of psychopathological structures preferable for schizophrenia; positive disorders, in their turn, act as «moderators» augmenting, amplifying manifestations of negative symptoms. This psychopathological construct of the correlation between dimensional structures paves a way for the development of a new concept of psychopharmacological treatment of schizophrenic deficit: both negative symptoms and amplifying positive symptoms are considered as «target symptoms» for pharmacological interventions.

[Effect of Lurasidone on symptoms of schizophrenia in five-factor dimensional model: pooled analysis of two short-term, randomized, double-blind, placebo-controlled studies in patients from Russia and Ukraine]

AIM

Evaluation of a new five-factor dimensional model of schizophrenia in recent revisions of classifications of mental disorders (DSM-5 and ICD-11) dictates the need to use this approach in conducting a comprehensive assessment of the effectiveness of new antipsychotic agents, including ethnically homogeneous populations of patients.

MATERIAL AND METHODS

Post-hoc analysis of pooled data from two randomized, double-blind, placebo-controlled, 6-week clinical studies (RCTs) of lurasidone (fixed doses, 40, 80, 120 or 160 mg/d) in patients experiencing an acute exacerbation of schizophrenia. Changes in PANSS total score, CGI-S score and five established PANSS factors were assessed using mixed-model repeated measures analysis.

RESULTS

Lurasidone (n=162, dose groups pooled) compared with placebo (n=68), significantly improved the PANSS total score at Week 6 (-23.0 vs. -10.5; p<0.001; effect size 0.82) as well as all PANSS factor scores: positive symptoms (-8.5 vs. -4.2; p<0.001; effect size 0.88), negative symptoms (-4.4 vs. -2.8; p=0.011, effect size 0.44), disorganized thoughts (-4.4 vs. -2.1; p<0.001; effect size 0.70), hostility/excitement (-2.7 vs. -0.7; p<0.001; effect size 0.66), and depression/anxiety (-3.5 vs. -2.2; p=0.002; effect size 0.53).

CONCLUSION

Lurasidone demonstrated significant improvement for both PANSS total score and each of the five PANSS factor scores, indicating effectiveness across the broad spectrum of schizophrenia symptoms. Effect size for both PANSS total score and each of the five PANSS factor scores for the local population was higher than for the wider population, which included patients from various countries.

Dopamine D3 receptor: A neglected participant in Parkinson Disease pathogenesis and treatment?

Parkinson disease (PD) is a neurodegenerative disorder characterized by motor and non-motor symptoms which relentlessly and progressively lead to substantial disability and economic burden. Pathologically, these symptoms follow the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) associated with abnormal α-synuclein (α-Syn) deposition as cytoplasmic inclusions called Lewy bodies in pigmented brainstem nuclei, and in dystrophic neurons in striatal and cortical regions (Lewy neurites). Pharmacotherapy for PD focuses on improving quality of life and primarily targets dopaminergic pathways. Dopamine acts through two families of receptors, dopamine D1-like and dopamine D2-like; dopamine D3 receptors (D3R) belong to dopamine D2 receptor (D2R) family. Although D3R's precise role in the pathophysiology and treatment of PD has not been determined, we present evidence suggesting an important role for D3R in the early development and occurrence of PD. Agonist activation of D3R increases dopamine concentration, decreases α-Syn accumulation, enhances secretion of brain derived neurotrophic factors (BDNF), ameliorates neuroinflammation, alleviates oxidative stress, promotes neurogenesis in the nigrostriatal pathway, interacts with D1R to reduce PD associated motor symptoms and ameliorates side effects of levodopa (L-DOPA) treatment. Furthermore, D3R mutations can predict PD age of onset and prognosis of PD treatment. The role of D3R in PD merits further research. This review elucidates the potential role of D3R in PD pathogenesis and therapy.

Widespread Changes in Positive Allosteric Modulation of the Muscarinic M1 Receptor in Some Participants With Schizophrenia

BACKGROUND

Preclinical and some human data suggest allosteric modulation of the muscarinic M1 receptor (CHRM1) is a promising approach for the treatment of schizophrenia. However, it is suggested there is a subgroup of participants with schizophrenia who have profound loss of cortical CHRM1 (MRDS). This raises the possibility that some participants with schizophrenia may not respond optimally to CHRM1 allosteric modulation. Here we describe a novel methodology to measure positive allosteric modulation of CHRM1 in human CNS and the measurement of that response in the cortex, hippocampus, and striatum from participants with MRDS, non-MRDS and controls.

METHODS

The cortex (Brodmann's area 6), hippocampus, and striatum from 40 participants with schizophrenia (20 MRDS and 20 non-MRDS) and 20 controls were used to measure benzyl quinolone carboxylic acid-mediated shift in acetylcholine displacement of [3H]N-methylscopolamine using a novel in situ radioligand binding with autoradiography methodology.

RESULTS

Compared with controls, participants with schizophrenia had lower levels of specific [3H]N-methylscopolamine binding in all CNS regions, whilst benzyl quinolone carboxylic acid-modulated binding was less in the striatum, Brodmann's area 6, dentate gyrus, and subiculum. When divided by subgroup, only in MRDS was there lower specific [3H]N-methylscopolamine binding and less benzyl quinolone carboxylic acid-modulated binding in all cortical and subcortical regions studied.

CONCLUSIONS

In a subgroup of participants with schizophrenia, there is a widespread decreased responsiveness to a positive allosteric modulator at the CHRM1. This finding may have ramifications it positive allosteric modulators of the CHRM1 are used in clinical trials to treat schizophrenia as some participants may not have an optimal response.

Antipsychotics: Mechanisms underlying clinical response and side-effects and novel treatment approaches based on pathophysiology

Antipsychotic drugs are central to the treatment of schizophrenia and other psychotic disorders but are ineffective for some patients and associated with side-effects and nonadherence in others. We review the in vitro, pre-clinical, clinical and molecular imaging evidence on the mode of action of antipsychotics and their side-effects. This identifies the key role of striatal dopamine D2 receptor blockade for clinical response, but also for endocrine and motor side-effects, indicating a therapeutic window for D2 blockade. We consider how partial D2/3 receptor agonists fit within this framework, and the role of off-target effects of antipsychotics, particularly at serotonergic, histaminergic, cholinergic, and adrenergic receptors for efficacy and side-effects such as weight gain, sedation and dysphoria. We review the neurobiology of schizophrenia relevant to the mode of action of antipsychotics, and for the identification of new treatment targets. This shows elevated striatal dopamine synthesis and release capacity in dorsal regions of the striatum underlies the positive symptoms of psychosis and suggests reduced dopamine release in cortical regions contributes to cognitive and negative symptoms. Current drugs act downstream of the major dopamine abnormalities in schizophrenia, and potentially worsen cortical dopamine function. We consider new approaches including targeting dopamine synthesis and storage, autoreceptors, and trace amine receptors, and the cannabinoid, muscarinic, GABAergic and glutamatergic regulation of dopamine neurons, as well as post-synaptic modulation through phosphodiesterase inhibitors. Finally, we consider treatments for cognitive and negative symptoms such dopamine agonists, nicotinic agents and AMPA modulators before discussing immunological approaches which may be disease modifying. This article is part of the issue entitled 'Special Issue on Antipsychotics'.